When blood vessels are damaged, cell fragments released from the bone marrow, called platelets, adhere to the walls of blood vessels and form clots to prevent blood loss. It is important to have adequate numbers of normally functioning platelets to maintain effective clotting, or coagulation, of the blood. Occasionally, when the body undergoes trauma, or when the platelets are unable to function properly, it is necessary to replace or transfer platelet components of blood into a patient. Most commonly, platelets are obtained from volunteer donors either as a component of a whole blood unit, or via plateletpheresis (withdrawing only platelets from a donor and re-infusing the remaining of the blood back into the donor). The platelets then are transferred to a patient as needed, a process referred to as “platelet transfusion.”
Platelet transfusion is indicated under several different scenarios. For example, an acute'blood loss, either during an operation or as a result of trauma, can cause the loss of a large amount of platelets in a short period of time. Platelet transfusion is necessary to restore a normal ability to control blood flow, or haemostasis. In a medical setting, an individual can develop a condition of decreased number of platelets, a condition known as thrombocytopenia. The condition can occur as a result of chemotherapy, and requires platelet transfusion to restore normal blood clotting.
Unlike red blood cells, which can be stored for forty-five (45) days, platelets can be stored for a few days. Platelet sterility is difficult to maintain because platelets cannot be stored at low temperatures, for example 4° C. to 5° C. A low storage temperature for the platelets initiates an activation process within the platelets that leads to aggregation and cell death. Bacterial growth in the platelet medium at suitable storage temperatures, e.g., room temperature, can lead to an unacceptable occurrence of bacterial contamination in platelets used for transfusion. In fact, bacterial contamination of platelet products has been recognized as the most frequent infectious risk from transfusion, occurring in approximately 1 of 2000 to 1 of 3000 whole blood derived random donor platelets or apheresis derived single donor platelets. In the U.S.A., bacterial contamination is considered to be the second most common cause of death overall, from transfusion, with mortality rates ranging from 1:20,000 to 1:85,000. As a result, the Food and Drug Administration (FDA) limits the storage time of platelets to five (5) days, thereby safeguarding the transfusion supply from bacterial contamination.
Many sterilization methods have been suggested. Platelet compositions typically can be sterilized by radiation, chemical sterilization, or a combination thereof. For example, a method of inactivating viral and bacterial blood contaminants using a quinoline as a photosensitizer is disclosed in U.S. Pat. No. 5,798,238. Other classes of photosensitizers are, for example, psoralens, coumarins, or other polycyclic ring compounds, as disclosed in U.S. Pat. No. 5,869,701; quinolones, as disclosed in U.S. Pat. No. 5,955,256; free radical and reactive forms of oxygen, as disclosed in U.S. Pat. Nos. 5,981,163 and 6,087,141; and phenothiazin-5-ium dyes, as disclosed in U.S. Pat. No. 6,030,767. U.S. Pat. No. 6,106,773 discloses another method for disinfecting biological fluids, including platelets, by contacting the biological fluids with an iodinated matrix material.
These sterilization methods, however, do not extend storage life of platelet but, on the contrary, appear to result in the significant loss of platelet function and reduction in the in vivo CCI (corrected count increment) and circulating half life by activating platelets. To effectively extend the shelf life of platelets, not only are sterilization methods for preventing contamination of the platelets important, but it also would be beneficial to provide improved methods to protect the platelets during the sterilization. It would also be beneficial to provide a convenient, effective platelet preservation composition for prolonging the shelf-life of the platelets, while maintaining the functionality and freshness of the platelets. In addition, it would be beneficial to provide a method or composition for storing platelets that requires less management of the surrounding platelet storage environment.